Department of Biological Sciences, Clemson University, Clemson, South Carolina 29634, USA; Eukaryotic Pathogens Innovations Center (EPIC), Clemson University, Clemson, South Carolina, 29634, USA.
Department of Genetics and Biochemistry, Clemson University, Clemson, South Carolina, 29634, USA; Eukaryotic Pathogens Innovations Center (EPIC), Clemson University, Clemson, South Carolina, 29634, USA.
Exp Parasitol. 2022 Dec;243:108410. doi: 10.1016/j.exppara.2022.108410. Epub 2022 Oct 26.
Entamoeba histolytica is a protozoan parasite that causes amoebic dysentery and amoebic liver abscess in humans, affecting millions of people worldwide. This pathogen possesses a two-stage life cycle consisting of an environmentally stable cyst and a pathogenic amoeboid trophozoite. As cysts can be ingested from contaminated food and water, this parasite is prevalent in underdeveloped countries and poses a significant health burden. Until recently there was no reliable method for inducing stage conversion in E. histolytica in vitro. As such, the reptilian pathogen, Entamoeba invadens, has long-served as a surrogate. Much remains unclear about stage conversion in these parasites and current treatments for amoebiasis are lacking, as they cause severe side effects. Therefore, new therapeutic strategies are needed. The genomes of these parasites remain enigmatic as approximately 54% of E. histolytica genes and 66% of E. invadens genes are annotated as hypothetical proteins. In this study, we characterized two hypothetical proteins in the Entamoeba species, EIN_059080, in E. invadens, and its homolog, EHI_056700, in the human pathogen, E. histolytica. EHI_056700 has no homolog in the human host. We used an RNAi-based silencing system to reduce expression of these genes in E. invadens and E. histolytica trophozoites. Loss of EIN_059080 resulted in a decreased rate of encystation and an increased rate of erythrophagocytosis, an important virulence function. Additionally, mutant parasites were more susceptible to oxidative stress. Similarly, loss of EHI_056700 in E. histolytica trophozoites resulted in increased susceptibility to oxidative stress and glucose deprivation, but not to nitrosative stress. Unlike the E. invadens mutants, E. histolytica parasites with decreased reduced expression of EHI_056700 exhibited a decreased rate of erythrophagocytosis of and adhesion to host cells. Taken together, these data suggest that these hypothetical proteins play a role in stage conversion, virulence, and the response to stress in the Entamoebae. Since parasites with reduced expression of EHI_056700 show decreased virulence functions and increased susceptibility to physiologically relevant stressors, EHI_056700 may represent a possible therapeutic target for the treatment of amoebiasis.
溶组织内阿米巴是一种原生动物寄生虫，可引起阿米巴痢疾和肝脓肿，影响全球数百万人。这种病原体具有一个两阶段的生命周期，包括环境稳定的囊和致病性阿米巴滋养体。由于囊可以从受污染的食物和水中摄入，因此这种寄生虫在欠发达国家很常见，对健康造成重大负担。直到最近，还没有可靠的方法在体外诱导溶组织内阿米巴的阶段转换。因此，爬行动物病原体 Entamoeba invadens 长期以来一直是替代物。这些寄生虫的阶段转换仍有许多不清楚的地方，目前的阿米巴病治疗方法缺乏，因为它们会引起严重的副作用。因此，需要新的治疗策略。这些寄生虫的基因组仍然神秘莫测，因为溶组织内阿米巴约有 54%的基因和 Entamoeba invadens 的 66%的基因被注释为假设蛋白。在这项研究中，我们对 Entamoeba 物种中的两个假设蛋白进行了表征，Entamoeba invadens 中的 EIN_059080 及其同源物 EHI_056700 在人类病原体溶组织内阿米巴中。EHI_056700 在人类宿主中没有同源物。我们使用基于 RNAi 的沉默系统来降低 E. invadens 和 E. histolytica 滋养体中这些基因的表达。EIN_059080 的缺失导致囊形成率降低和红细胞吞噬作用率增加，这是一种重要的毒力功能。此外，突变寄生虫对氧化应激更敏感。同样，E. histolytica 滋养体中 EHI_056700 的缺失导致对氧化应激和葡萄糖剥夺的敏感性增加，但对亚硝化应激没有影响。与 E. invadens 突变体不同，E. histolytica 寄生虫中 EHI_056700 表达降低导致红细胞吞噬作用和与宿主细胞的粘附率降低。总之，这些数据表明这些假设蛋白在 Entamoebae 的阶段转换、毒力和对压力的反应中发挥作用。由于表达降低的寄生虫表现出降低的毒力功能和对生理相关应激源的敏感性增加，EHI_056700 可能是治疗阿米巴病的潜在治疗靶点。
